Pool Winterization Calculator

Shock Chlorine is calculated by raising your Current Chlorine level up to a 12 ppm winterizing target, using the rule of thumb that roughly 2 oz of calcium hypochlorite per 10,000 gallons raises chlorine by 1 ppm — so it scales with both Pool Volume and how far below target your Current Chlorine already sits. Which input matters more depends on where your Current Chlorine already sits: Shock Chlorine is proportional to Pool Volume times the gap between your reading and the 12 ppm target, so below about 6 ppm a percentage change in Pool Volume moves the dose more, while above 6 ppm — where the gap is already small — the same percentage change in Current Chlorine moves it more. At a 10 ppm starting reading, a 10% change in Current Chlorine swings the dose roughly five times as far as a 10% change in Pool Volume. Current pH and Current Alkalinity feed into Water Balance Check, a readiness flag for whether both readings sit inside the 7.2–7.6 and 80–120 ppm windows real pool-closing guidance recommends before closing — but neither number changes the Shock Chlorine, Winter Algaecide, Pool Antifreeze, or Cover Size amounts themselves. Pool Antifreeze is based on a fixed count of plumbing lines by Pool Type (more lines assumed for inground pools) rather than on Pool Volume, so a larger inground pool with the same number of return and skimmer lines needs the same antifreeze as a smaller one.

Cover Size is estimated from Pool Volume by assuming an average depth that follows Pool Type — 5 feet for inground pools, 4 feet for above-ground pools, since an above-ground pool's water line typically sits lower — to back out surface area, then adding the standard 4 feet of overlap to each dimension. It is an area figure for budgeting only: covers are ordered by dimensions, so measure your actual length and width and add 4 feet to each before you buy. Estimated Chemical Cost values the three chemicals at $4 per pound of calcium hypochlorite shock, $0.75 per ounce of polyquat winter algaecide (about $24 for a 32 oz quart) and $8 per gallon of pool antifreeze. These are typical 2026 retail figures, not a quote — substitute your own supplier's prices for a real budget. Pool Volume stays in US gallons regardless of the site-wide unit setting, because every chemical dose on this page is US-customary and there is no clean way to convert pounds, ounces, and gallon-jug counts to metric alongside it.